B vitamins can be tricky. Too much of one may suppress the others. B12 works with folic acid so too much B12 could have an adverse effect. B vitamins are much like minerals in that there are antagonist and agonist situations. B2 is overlooked and is very helpful for the immune system.
There are some "balanced b vitamins" meaning they put the optimal ratios in them. I think Country Life had this, at least last time I checked. There are also co-enzymated b vitamins which help metabolize easier.
You might want to look at the benefits of taurine which are low in diabetes and also supports liver function. Amino acids can also have the same effect as listed above.